Window elevator systems as known in the art, comprise a window, clamping parts holding the window, guiding parts (fixed elements or small wheels) over which the cable is bend in order to guide the cable in a defined direction, a driving drum and a transmission member. The transmission member transfers the rotating movement of the driving drum to the window. Usually, a known transmission member comprises a galvanized steel cable, which moves inside a casing. Such casing is usually a steel casing, coated with a polymeric coating. Between the galvanized steel cable and the inner side of the steel casing, a polymer inner liner is placed, being a polymer tube, fitting closely with the inner side of the steel casing.
Galvanized steel cables, being part of such transmission member, have to meet several requirements, such as a high corrosion resistance (simulated by means of the so-called “salt spray test”), a temperature stability in the temperature range from −40° C. up to 90° C. or even up to higher temperatures for a short period of time, high tensile strength and a good fatigue resistance. Requirements which are to be met in order to provide systems which function during the whole life-time of the vehicle.
Further, the weight of the steel cord, and of the transmission member as a whole, is to be as low as possible. The cable of the transmission member is to be bend in curvatures having decreasing bending radii. Such curvatures are found at the guiding parts of the window elevator system, over which the cable is to be bend. These decreasing bending radii require cables with increased flexibility and fatigue resistance. Finally, the cable has to have a minimum of permanent elongation, after being subjected to an elongating force. Too much permanent elongation leads to incorrect closing and opening of the windows, and a cable which runs off the guiding parts of the system, since the cable looses its tensioning around these guiding parts.
Several attempts have been made to provide a solution to all above-mentioned problems simultaneously, however with little result.
Cables used for control cable applications or other static or dynamic applications have to have also limited permanent elongation and are subjected to similar if not identical requirements.
Also in other applications, relatively small cables have to have a very limited permanent elongation. E.g. cables used to open and close breaks of scooters, bicycles and other vehicles, preferably have no or very small permanent elongation. If the permanent elongation is too large, inadequate displacement of the connected elements of the breaks may occur.